Where equipment such as air handling units is placed on the roof of a building, various pipes, cables, and conduits will have to be run to the equipment. In a similar manner cables and wiring to antennas and other structures are run across the roof. Most building codes require that these pipes, cables, etc. be raised above the surface of the roof, typically at a height of 10 to 12 inches above the surface. Multiple supports will be needed, spaced along the length of the item being supported. The number and spacing of the supports will depend on the stiffness of the item.
Often, the roof over which the pipe is run will be uneven. This may be due to irregularity in the underlying structure; bulging in the roofing material; or stepped levels of the roof itself. It may be necessary for the pipe to be run level or at a consistent slope which is unaffected by the unevenness of the roof. This requires supports which can vary the height at which they support the pipe or cable. Some of the supports currently available are not adjustable. The use is this type of support can result in unsupported spans or, in extreme cases, a support dangling from a pipe rather than supporting it. Examples of fixed height supports are disclosed in U.S. Pat. Nos. D353,894 and D367,329 to Nelson et al. and 5,072,901 to Scott.
Two common approaches to providing an adjustable support are stackable stands, which provide incremental height changes and threaded adjustment built into the stand. The height increments provided by the stackable approach may not provide the degree of adjustment needed. The designs which utilize threaded adjustment are typically heavy and/or large. Weight and size are especially important where large numbers of supports are used. A business which uses such stands regularly must store large numbers of stands. All users will have to ship the stands to the job site and then transport them to the rooftop.
U.S. Pat. No. 4,513,934 to Pruyne discloses a stackable design. U.S. Pat. Nos. 4,445,656 to Leitch, 5,217,191 and 5,685,508 to Smith, and 5,040,751 to Holub disclose various forms of supports with threaded adjustment. The Smith designs, in particular, utilize a heavy concrete base.
U.S. Pat. No. 4,033,534 to Bergkvist discloses an approach in which height variation is achieved by embedding the lower end of the support in a cast material, such as concrete at the time of installation. This approach has the shortcoming that it can not be adjusted at a later time.
Applicants have sold a previous version of the present invention in which the support member was attached to the base, and the strap was attached to the support, at the time of manufacture. Both sheet metal screws and spot welding were found to be satisfactory methods of attachment. While functional, and providing adjustability, the stand could not be shipped in a knock-down configuration, and required tools for assembly. This resulted in inefficient storage and shipping of the stand as the assembled stand occupies significant space.
Most of the existing designs require tools or supplemental fasteners to assemble or adjust. The tools may not be immediately available, and fasteners easily become lost or are dropped.
There is a need for an adjustable stand which provides fine variations in support height; which is compact to store and ship and is low in weight. The stand should be capable of being shipped and stored in a knocked down form, and assembled on the rooftop at the job site, by unskilled labor, without the use of tools or additional fasteners. The range of variation in support height should be at least +/-2 inches to accommodate different building code requirements and unevenness in roof height. Additionally, the stand should be inexpensive to manufacture.